Protractor.



lio. 789,044. PATENTED MAY 2, 1905. 0. E. MENTZBR.

PROTRAGTOR. APPLIOATION FILED JULY so, 1903.

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No. 789,044. PATENTED MAY 2, 1905. G. E. MBNTZER.

PROTRAGTOR.

APPLIOATION FILED JULY a0, 1903.

2 SHEETS-SHEET 2.

Witnesses avwe ntoz Nrrn STATES Patented May 2, 1905.

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PROTRACTOR.

SPECIFICATION forming part of Letters Patent No. 789,044, dated May 2, 1905.

Application filed July 30,1903. Serial No. 16 7,620.

To nil whom it may concern:

Be it known that .l, CLARENCE E. MENTZER, a citizen of the United States, residing at Hagerstown, in the county of Washington and State of Maryland, have invented certain new and useful Improvements in Protractors, of which the following is a specification.

My said invention consists in an improved construction of protractors for attachment to and use in connection with an ordinary T- square or parallel ruler on a drawing board or table of common construction whereby a very convenient instrument of such a character is provided and one which is adapted for use with any kind of ruler and the blades whereof may be interchanged and are adapted for various adjustments, all as will be hereinafter more fully described and claimed.

Referring to the accompanying drawings, which are made a part hereof, and on which similar reference characters indicate similar parts, Figure 1 is a top or plan View of my improved protractor when attached to the ruler and ready for use; Fig. 2, a central transverse section of the same on the dotted line 2 2 in Fig. 1; Fig. 3, an under side plan View of the instrument as shown in Fig. 2, and Figs. 4:, 5, and 6 detail views illustrating the particular construction of the several parts indicated.

In said drawings the portion marked A represents the frame of the instrument, B an oscillating disk or center portion thereof, and C the protractor-blades.

The frame A is preferably of metal, but may be of any suitable material and of suitable form for the purpose, provided with a central aperture in which the disk B is mounted. It is provided with extensions a, extending from opposite sides and having wheels 1 journaled on stud-shafts 2, which are mounted in and carried by said extensions. Said wheels are each provided with a flange, as shown, to engage the edge of the ruler. Plates or shoes 3, with upwardly-curved edges, are also mounted on the lower ends of the shafts beneath said wheels to enable the instrument to slide freely over the work. A plate A is secured rigidly to the under side of the frame A by means of screws 4 and nuts 5 and has an extension extending to the center of the frame and provided with a bearing a to receive the pivot of disk B. An adjustable frame A, consisting, preferably, of a rod or wire bent to a suitable form, is attached to the frame A by .means of slotted screws 6, (see Fig. 6,) which project through apertures alongside the wheels 1 and are provided with nuts 7 on their upper sides. The branches of said frame A extend through the slots of said screws and rest upon the top surface of frame A, against which they are clamped by means of said thumb-nuts 7. On the outer end of frame A is mounted a flanged wheel 8 on the stud-shaft 9, and a shoe 10 is mounted on the lower end of said shaft beneath said wheel, said parts being in all respects similar to the corresponding parts 1, 2, and 3 on frame A. By means of said wheels 1 and 8, which engage opposite edges of the ruler R, the instrument is secured to said ruler, so that it may slide freely back and forth thereon. The frame A being adjustably secured to the frame A, as described, the instrument is adapted for adjustment to rulers of varying widths.

The diskBis adapted to carry the protractor-blades and is provided with a central pivot or stud I), which is preferably formed with a flanged head 72 and is secured to the center of the disk by a screw Z). It is mounted in the bearing 0 provided therefor in the inwardlyextending arm of plate A Said disk is adapted to fit snugly within the central aperture in frame A and oscillate on said pivot. On one side it is provided with a barrel or casing 7), in which is mounted a sliding locking-bolt I), said locking-bolt extending through an aperture in the disk and being adapted to engage with one of the series of apertures 11 in the plate A A knob B is mounted in the center of said disk for convenience in turning the same. A push-button 19. is mounted in a central aperture in said knob and engages with the inner end of the operating-lever 13, the outer end of which projects through the slot in the adjacent side of the casing b and engages with the locking-bolt b. The end of said lever engaging the locking-bolt is normally held down by a spring 14 and is adapted to rock on the fulcrum 15. By this means said locking-bolt is withdrawn from engagement with one of the apertures 11 in plate A by pressing the push-button 12, when the disk will be free to rotate on its pivot to the point desired by the operator. Upon releasing said push-button the spring will operate said locking-bolt into engagement with one of said apertures 11 and lock the disk in the desired position. A scale is provided around a portion of the edge of disk B, and an indicatorpoint 0 is provided on the frame, as indicated in Fig. 1, so that the user may readily set the protractor-blades to any angle desired. A sleeve b of the form shown in Fig. 1 is mounted around the casing 6, being provided with a vertical slot to pass over the lever 13 and with transverse notches extending each way from said slot near the bottom, leaving a projecting point or finger b on each side adapted to project under said lever when said sleeve is turned in either direction, and thus hold the locking-bolt 5 free from engagement with the plate A permitting the disk to rotate freely and be stopped at any point desired. A quadrant-shaped plate'19 is secured to the under side of disk B at its front edge. The edges of said quadrant form bearings for one side of the shanks of the protractor-blades. Said plate has an extension on its front edge which projects beyond the edge of frame A and is provided with a perforation in which ismounted a stud 16. A cam-lever 17 is pivoted to the top of said stud, and a washer 18, which projects over the top edge of frame A, is interposed between said cam-lever and said plate. By this means the turning of the camlever to the position shown in Fig. 2 will operate to clamp frame A between washer 18 and plate 19 and secure the disk in any desired adjustment, as when it is stopped at points which will bring locking-bolt Z) between any two of the perforations 11 in plate 2.

The protractor-blades C may be of any form or material desired, and each is mounted upon a suitable shank C, which is adapted to fit between one edge of the quadrant 19 and a head 20 of a clamping-bolt 21, mounted in a suitable perforation in disk B and provided on its upper end with a thumb-nut 22 for adjusting the same. The edges of said shanks and also of quadrantand heads 20 are slightly tapered, as shown in Fig. 5, so that each shank when in position fits in what is practically a dovetail groove. By turning thumbnut 22 to draw the head 20 tightly against said shank its tapered edge is forced firmly against the edge of the quadrant, and thus held in a true angle in relation to the opposite blade. The blades 0 are preferably secured to the shanks C by means of screws 0 and 0 projecting through the respective parts. Said screws 0' preferably extend through transverse slots in said shank C to permit said blades to be easily adjusted to a true angle in relation to each other.

In use the instrument is mounted on the ruler or T-square R, as shown in Figs. 1 and 3, and is thus adapted to move freelylongitudinally of said ruler. Cam-lever 17 being in the position indicated by dotted lines in Fig. 2 and the locking-sleeve 6 being in the position to permit locking-bolt I) to engage with the perforations in plate A the operator by pressing the push-button 12 is permitted to turn disk B, carrying the protractor-blades from one degree to another, when bolt 6' is permitted to engage one of the perforations 11 and secure said parts so that the protractor-blades will extend at an angle of any degree desired. When an angle between those indicated by the perforation 11 is desired, sleeve 6 is turned to hold locking-bolt 6 free from plate A and the cam-lever is used to secure the parts in the position desired, as above described.

By this means a protractor is provided which can be quickly and easily attached to a ruler or T-square of any width without disturbing the connection between the ruler and the drawing-table and which enables the draftsman to secure every'possible angle quickly and conveniently. The blades being removable, different kinds of blades may be used interchangeably adapted for different kinds of work, as will be readily understood.

Having thus fully described my said invention, what I claim as new, and desire to secure by Letters Patent, is

1. A protractor for attachment toan ordinary ruler, comprising the frame carrying the protractor-blades, wheels journaled thereon adapted to engage with one edge of the ruler and an adjustable frame secured to said protractor-frame carrying a wheel adaptedto engage with the opposite edge of said ruler, substantially set forth.

2. A protractor comprising a frame with an annular opening, a disk carrying the protractor-blades mounted to oscillate in said opening, wheels mounted on said frame adapted to engage with one edge of the ruler, another wheel carried by a frame adjustably secured to said first frame and adapted to engage with the opposite edge of said ruler, substantially set forth.

3. A protractor comprising a frame, parts arranged on said frame adapted to engage one edge of an ordinary ruler, a second frame adjust-ably secured to the first carrying means for engaging the opposite edge of said ruler, whereby said protractor may be secured on said ruler to slide longitudinally'thereof, an oscillating disk mounted in the main frame, the protractor-blades removably secured to said disk, and means for locking said disk in the desired adjustment.

4. In a protractor, the combination of the annular frame, a plate secured. to its under side having a bearing central with the opening therein, a disk mounted in said central opening and provided with a pivot which engages with said bearing, a locking catch or bolt carried by said disk and adapted to engage with one of the series of perforations in said plate, and protractor-blades secured to and carried by said disk, substantially set forth.

5. In a protractor, the combination of the annular frame, the central disk pivoted therein, locking means for securing said disk in the position desired a quadrant-shaped, plate secured to the under side of said disk, clampingbolts mounted in said disk adjacent to the edges of said quadrant, and protractor-blades provided with shanks mounted between the edges of said quadrant and the heads of said clamping-bolts, substantially set forth.

6. In a protractor, the combination of the annular frame, the oscillating disk mounted therein, a quadrant-shaped plate with tapered edges mounted on the front side of said disk, clamping-bolts adjacent to the edges of said quadrant provided with tapered heads, and protractor-blades provided with shanks having tapered edges mounted between the edges of said quadrant and the heads of said bolts, substantiallyset forth.

7. In a protractor, the combination of the annular frame, the oscillating disk carrying the protractor-blades mounted therein, and a cam-lever carried by said disk and adapted to engage said annular frame for securing the parts in adjusted position, substantially set forth.

8. In a protractor, the combination of the annular frame, the oscillating disk mounted therein, the locking-bolt carried by said disk and adapted to engage with one of the series of perforations in a part of said frame, a lever for operating said bolt, a central operatingknob, and a push-button mounted centrally in said knob for engaging said lever and operating said lockingbolt, substantially set forth.

9. In a protractor, the combination of the annular frame carrying the oscillating center having protractor-blades mounted thereon, an adjustable frame secured to said annular frame carrying a flanged wheel to engage one edge of the ruler, other similar wheels mounted on said annular frame to engage the opposite edge of said ruler, and shoes with upwardly-curved edges mounted beneath said wheels, substantially set forth.

In witness whereof I have hereunto set my hand and seal, at Hagerstown, Maryland, this 16th day of July, A. D. 1903.

CLARENCE E. MENTZER. [L.s.]

Witnesses:

DANIEL STOVER, WM. L. SGHLEIGH, Jr. 

